The dial caliper is a versatile measuring instrument. It is capable of taking inside, outside, depth, and step measurements. It can measure these dimensions from 0 to 150 mm in increments of 0.02 mm, or in standard units up to 0.0005 inch. The standard dial caliper features a depth scale, bar scale, dial indicator, inside measurement jaws, and outside measurement jaws. The bar scale is divided into one-tenth (0.10) of an inch graduations. The dial indicator is divided into one-thousandth (0.001) of an inch graduations. Therefore, one revolution of the dial indicator needle equals one-tenth of an inch on the bar scale (one hundred thousandths of an inch equals one-tenth of an inch).
The metric dial caliper is similar in appearance to the standard (inch-reading) model. However, the bar scale is divided into 2 mm increments. Additionally, on the metric dial caliper, one revolution of the dial indicator needle equals 2 mm. Both standard and metric dial calipers use a thumb-operated roll knob for fine adjustment. When you use a dial caliper, always move the measuring jaws backward and forward to center the jaws in the work. Make sure that the caliper jaws lay flat on the work. If the jaws or the work are tilted in any way, you will not obtain an accurate measurement. However, although dial calipers are precision measuring instruments, they truly are only accurate to within 60.002 inch. The factors that limit dial caliper accuracy include jaw flatness and “feel.” Micrometers are better suited to measuring tasks that require high precision.